When fishing, it is sometimes desirable to know the length of line which is out. For example, sometimes a fisherman needs to cast his line out a specific distance from the boat or to a known depth. Also, when reeling in a fish, the fisherman may want to know how far the fish is from the boat when "playing" the fish.
In the past, various types of mechanical devices have been used to measure the length of the fishing line. One such device employs a wheel positioned in rolling contact with the fishing line which operates a mechanical counter. The wheel is rotated in a first direction as the line is cast out to increment the mechanical counter. The wheel rotates in the opposite direction when the line is reeled in to decrement the counter. The circumference of the wheel is typically proportional to the unit of length being measured. Such prior art devices are disclosed in the patents to Call, U.S. Pat. No. 4,382,336; Abdo, U.S. Pat. No. 3,839,798; and Demchak et al., U.S. Pat. No. 4,285,131.
One disadvantage with mechanical counters is that such counters increase the amount of drag on the fishing line. The increased drag will reduce the distance over which the line is cast. Further, the increased drag will cause extra tension on the line which may result in the line breaking while trying to reel in a fish. Another drawback is that the fishing line may slip with respect to the surface of the wheel. When slippage between the fishing line and the surface of the wheel occurs, there may be significant errors in the length of the fishing line being measured.
Another approach which has been tried in the past is to use a sensor to detect rotation of the spool in the fishing reel, and a microcomputer to calculate the length of line based on the number of spool revolutions. This method, however, does not provide a direct measure of the amount of line which is paid out. Instead, the length of line is only estimated. Because different amounts of line are paid out during each revolution of the spool it is difficult to estimate the length of the line. Thus, such devices do not provide a high degree of accuracy.